true reading is therefore four degrees and four-tenths. This reading,
however, must be corrected, because the original volume instead of
being 200 cubic centimeters, is 235 cubic centimeters. The actual
percentage of sugar in the sample examined is obtained by the following
proportion:
200 : 235 = 4.4 : _x_.
The correct reading is therefore 5°.2, the percentage of sugar in the
sample examined.
The results obtained by the method just described may vary somewhat
from the true percentage by reason of the variation of the content
of fiber in the bagasse. It is, however, sufficiently accurate for
technical control in sugar factories and on account of its rapidity
of execution is to be preferred for this purpose. More accurate
results would be obtained by drying the bagasse, and proceeding with
the examination in a manner entirely analogous to that described for
the extraction of sugar from dried canes by aqueous alcohol. In both
instances the reducing sugar is determined in the manner already
mentioned.
=215. Determination of Fiber in Cane.=—In estimating the content
of sugar in canes by the analysis of the expressed juices, it is
important to make frequent determinations of the fiber for the purpose
of obtaining correct data for calculation. In periods of excessive
drought, or when the canes are quite mature, the relative content of
fiber is increased, while, on the other hand, in case of immature
canes, or during excessive rainfalls, it is diminished. The chief
difficulty in determining the content of fiber in canes is found in
securing a representative sample. On account of the hard and fibrous
nature of the envelope and of their nodular tissues, canes are reduced
to a fine pulp with great difficulty by the apparatus in ordinary
use. A fairly homogeneous pulp, however, may be obtained by means of
the shredder described on page 9. The canes having been shredded as
finely as possible, a weighed quantity is placed in any convenient
extraction apparatus and thoroughly exhausted with hot water. The
treatment with hot water should be continued until a few drops of the
extract evaporated on a watch glass will leave no sensible residue.
The residual fiber is dried to constant weight at the temperature of
boiling water, cooled in a desiccator and rapidly weighed and the
percentage of fiber calculated from the data obtained. On account of
the great difficulty of securing a homogeneous pulp, even with the best
shredding machines, the determination should be made in duplicate or
triplicate and the mean of the results entered as the percentage of
fiber. The term fiber as used in this sense, must not be confounded
with the same term employed in the analysis of fodders and feeding
stuffs. In the latter case the term is applied to the residue left
after the successive treatment of the material with boiling, dilute
acid and alkali. The analysis of canes for feeding purposes is
conducted in the general manner hereinafter described for fodders.
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